Long-acting Thyroid Stimulator Research Articles

The Biphasic Stimulatory and Inhibitory Effects of Concanavalin A on Thyroid Activation Induced by Thyrotropin

Concanavalin A (Con A) was tested for its ability to affect thyroid activation induced by TSH in mouse thyroid lobes. Pretreatment of thyroid lobes with Con A at concentrations from 1.55--400 microgram/ml was found to have biphasic stimulatory and inhibitory effects of the TSH-induced accumulation of cAMP and formation of colloid droplets. Low concentrations of Con A potentiated TSH activation of thyroidal formation of cAMP and endocytosis. In contrast, higher concentrations of Con A markedly inhibited these TSH effects. The inhibitory effects observed after preincubation with Con A were abolished by the addition of alpha-methyl-D-glucoside to the incubation medium. A high concentration of Con A also inhibited cAMP formation induced either by prostaglandin E2 or the long-acting thyroid stimulator. However, the basal and TSH-stimulated glucose oxidation in mouse thyroid lobes was not depressed by a high concentration of Con A. Uptake of 125 I-labeled Con A by thyroid tissues increased with time up to 1 h and was directly proportional to tissue weight. These findings suggest that the specific interaction between Con A and its receptors may lead to conformational changes in the structure of the membranes of the thyroid follicular cells which facilitate TSH-induced thyroid hormone secretion via the adenylate cyclase-cAMP system.

Pretibial Myxoedema: A Clinical and Pathological Study

Summary: Long acting thyroid stimulator (LATS) has been implicated in the pathogenesis of pretibial myxoedema (PTM). The objective of the present study was to seek evidence for a pathogenic role for LATS in PTM by immunofluorescent antibody study of skin biopsies from these lesions.Six patients (five males and one female) with PTM were studied; one had associated thyroid acropachy. Four were thyrotoxic on presentation, one was euthyroid and the sixth hypothyroid.Immunofluorescent antibody studies showed no difference in the deposition of immunoglobulin G (IgG) in the skins from PTM compared to normal skins adjacent to the lesions, skins of thyrotoxic controls without PTM, and skins of “normal control” subjects.The results gave no support to the hypothesis that PTM results from a local antigen‐antibody tissue reaction.

Influence of indomethacin and of polyphloretin phosphate fractions on in vivo secretion of thyroid hormone in mice.

ABSTRACT Previous in vivo studies in mice have shown that polyphloretin phosphate (PPP), a polyionic polyester of phosphoric acid and the dihydrochalcone phloretin, can inhibit thyroid hormone secretion induced by TSH and by the long-acting thyroid stimulator of Graves' disease (LATS), but not that induced by catecholamines or 5-hydroxytryptamine (5-HT). The present study was undertaken to explore further the mechanism of this effect, particularly the possibility that PPP interferes with the synthesis of endogenous prostaglandins (PG). Therefore, the effects of PPP and some of its subfractions and congeners were compared with those of indomethacin, a known inhibitor of PG synthesis, with respect to their influence on the blood radioiodine (BRI) increase in response to TSH, 5-HT, and isoprenaline (IPNE) in 125I- and T4-pre-treated mice. When given alone, neither indomethacin nor PPP or its subfractions reduced the BRI levels. Instead, small increments were seen in occasional experiments. Indomethacin did not inhibit the BRI increase in response to any of the thyroid-stimulating agents, but rather enhanced the responses in occasional experiments. PPP and some of its high-molecular weight subfractions reduced the BRI increases in response to TSH but not those to 5-HT or IPNE. The findings do not support the concept that de novo synthetized PG mediates TSH activation of thyroid hormone secretion, but they favour the view that PPP inhibits the action of TSH at its receptor site.

Methods for separation of long-acting thyroid stimulator (LATS) from sera containing LATS and TSH

Methods were devised for separation of long-acting thyroid stimulator (LATS) from TSH in serum containing both thyroid stimulators by using Rivanol, concanavalin A (con A), or staphylococcal protein A. When 3–5 volumes of 0.5% Rivanol solution were mixed to serum containing TSH or LATS activity, LATS activity remained mainly with IgG in the supernatant fraction. On the contrary, TSH activity was precipitated. When 10 mg con A was added to 1 ml test serum, almost all TSH activity was precipitated, but LATS activity remained in the supernatant fraction, which consisted mainly of IgG and albumin. Almost all LATS activity and part of the TSH activity were precipitated by addition of more than 7.5% polyethylene glycol (PEG), which was therefore not useful for separation of the stimulators in serum. Affinity chromatography on staphylococcal protein A-Sepharose was also found to separate the two thyroid stimulators in serum. By this method LATS-immunoglobulin bound to the protein A column, but no binding of the biologic and immunologic activity of TSH was observed. The protein A method seems the most useful of these four methods for complete separation of both stimulators.

Thyrotropin Binding and Long Acting Thyroid Stimulator Absorbing Activities in Subcellular Fractions from Isolated Thyroid Cells and Thyroid Homogenates

The ability of various thyroid subcellular fractions to bind [125I]iodo TSH and to absorb long-acting thyroid stimulator (LATS) and thyroid stimulating immunoglobulins (TSI) activities was examined. Membranes purified from thyroid homogenates or isolated thyroid cells absorbed LATS/TSI activities and specifically bound [125I]iodo TSH. Purified thyroglobulin, nuclei, mitochondria and ribosomes did not bind [125I]iodo TSH nor did they absorb LATS/TSI activities. Cell sap obtained by gentle lysis of isolated thyroid cells failed to absorb LATS/TSI activities and to bind labeled hormone. However, freeze-thawing of the cells fragmented the membranes, releasing [125I]iodo TSH binding as well as LATS/TSI absorbing activities into the soluble (cell sap) fraction. The results suggest that the LATS/TSI antigen is of cell surface origin, includes the TSH receptor or larger membrane fragments containing the receptor, and that its release into the soluble fraction is due to the fragmentation of the thyroid membrane during homogenization and preparative procedures.

Active transport of iodide in isolated porcine thyroid cells. Application to an in vitro bioassay of thyrotropin

Porcine thyroid cells were cultured for 2 days with or without dibutyryl cyclic AMP or thyrotropin (TSH). Then they were isolated post-culture by a gentle treatment with a calcium chelating agent. Some characteristics of the iodide transport system were studied in these thyroid cell suspensions. Iodide influx is a saturable, temperature- and energy-dependent phenomenon. It is blocked by ouabaïn, N-ethylmaleimide, dinitrophenol, cardiotoxin, low Na + concentration and harmaline. Only 3% of the intracellular iodide is trichloracetic-acid-insoluble at equilibrium. The apparent Michaelis constant ( K m) of the transport system is 30 μM. For monolayer cells, the decrease of C/M ratio, increase of apparent K m, and decrease of V max between day 0 (freshly isolated cells) and day 6, indicate a loss of iodide-trapping ability up to passive diffusion. To the contrary, high values of C/M and normal K m (30 μM) are observed in TSH follicles from reassociated cells. At iodide equilibrium, thryotropin, prostaglandins E 1 and E 2 and long-acting thyroid stimulator (LATS), induce a fast release of iodide. This release is dose-dependent in the first 5 min. It has been used to develop a bioassay of TSH and a fast detection of LATS.

Neonatal thyrotoxicosis associated with the hyperviscosity syndrome

Baby S.M. was the 2,230-gram, 36-week product of a 28-yearold gravida 1 para 0 black woman with a previous history of hyperthyroidism, treated by subtotal thyroidectomy one year prior to her pregnancy. Clinically, she was euthyroid, with a normal T, value and a negative long-acting thyroid stimulator titer. No thyroid or anti-thyroid medications were taken during pregnancy. Labor and delivery were uneventful Shortly after birth, however, the infant developed acrocyanosis, tachypnea (100/ minute), tachycardia (180/minute), and hyperactivity with marked irritability and tremulousness. At 13 hours of age, his blood glucose value, measured by Dextrostix, was 25 mg/dl; 10% dextrose solution was administered intravenously, and he was transferred to St. Louis Children's Hospital. On arrival, he was moderately icteric (total bilirubin 10.4 rng/dl; direct bilirubin 2.52 mg/dl) and was noted to have generalized petechiae, purpura, and hepatosplenomegaly. Diffuse cardiomegaly was noted radiographically; right heart enlargement was shown electrocardiographically. Sixty percent inspired oxygen was required to maintain normal arterial blood gas values. Serum calcium was decreased to 6.8 mg/dl, but the concentrations of the other electrolytes were normal. Venous microhematocrit was 73%. Initial platelet count was 170,000/ mm', but it fell to 56,000/mm :~. Blood smear revealed 2,880 nucleated red blood cells/mrn ~, but was otherwise unremarkable.

The possible relation between postpartum exacerbation of hyperthyroidism and neonatal thyrotoxicosis.

Hyperthyroidism is generally considered to be ameliorated during pregnancy, and there appears to be a high incidence of postpartum exacerbation. These phenomena have to our knowledge not been related to neonatal thyrotoxicosis, a transient hyperthyroidism seen only in newborns of previous or current hyperthyroid mothers. The first of two siblings of a previously thyrotoxic mother had marked symptoms of neonatal thyrotoxicosis and high levels of thyroid hormones. The mother had not received antithyroid treatment during her first pregnancy. During her next pregnancy she was treated with propylthiouracil from the second trimester. This infant had only minimal thyrotoxic signs but almost as high levels of thyroid hormones during the neonatal period as the elder. The mother had no signs of postpartum exacerbation but her thyroid hormones were significantly elevated in the postpartum period analogous to the infants. Neither the mother nor the infants presented any increase in thyroid-stimulation hormone and long-acting thyroid stimulator during the hyperthyroid periods. The possibility is discussed, that postpartum exacerbation of hyperthyroidism and neonatal thyrotoxicosis may be related. They could be the result of a changed balance between a thyroid stimulator and an inhibitor after birth.

Thyroid carcinoma and concurrent hyperthyroidism: a study of ten patients.

Ten patients with thyroid carcinoma and co-existing thyrotoxicosis have been studied. In six patients thyroid carcinoma was suspected before thyroidectomy. In three of the four patients in whom neoplasia was not suspected before operation, the lesion was a small papillary carcinoma. In only one of the eight patients in whom serum long acting thyroid stimulator (LATS) and long acting thyroid stimulator protector (LATSP) were assayed was detectable activity found, a low incidence. The possible role of hyperthyroidism in initiating thyroid malignancy is discussed.

Evidence for the Existence of a Histamine H2-Receptor in the Mouse Thyroid

The existence of a histamine H2-receptor in the thyroid was investigated. Histamine in vitro stimulated the formation of cyclic AMP and colloid droplet formation in mouse thyroid lobes. Stimulation by histamine of cyclic AMP formation in mouse thyroid lobes was significantly inhibited by metiamide, a histamine H2-receptor antagonist. 4-Methylhistamine, a histamine H2-receptor agonist, markedly stimulated cyclic AMP formation, whereas 2-methylhistamine, a histamine H1-receptor agonist, was ineffective. The stimulation by 4-methylhistamine of cyclic AMP formation was markedly inhibited by metiamide, but not by chlorpheniramine, a histamine H1-receptor antagonist. In contrast, metiamide did not affect cyclic AMP formation induced either by TSH or by the long-acting thyroid stimulator. Therefore, it is suggested that there exists a histamine H2-receptor in the membranes of the thyroid follicular cells which facilitate thyroid hormone secretion via the adenylate cyclase-cyclic AMP system.

The Inhibitory Effect of Acute Administration of Excess Iodide on the Formation of Adenosine 3′,5′-Monophosphate Induced by Thyrotropin in Mouse Thyroid Lobes

In a previous paper, we demonstrated that an inhibitory action of excess iodide on thyrotropin-induced thyroid hormone secretion occurs at a site subsequent to the generation of cyclic AMP. In the present study, however, we have found that thyroidal cyclic AMP formation induced by thyrotropin in vitro was markedly inhibited by the acute administration of excess iodide to mice fed a low iodine diet. In contrast, excess iodide failed to produce inhibition in animals fed a regular diet. In vitro stimulation by long-acting thyroid stimulator (LATS), prostaglandin E2, and 4-methylhistamine of cyclic AMP formation in mouse thyroid lobes was also significantly inhibited by the acute in vivo administration of excess iodide. The inhibition was completely relieved by the administration of methimazole prior to excess iodide. Furthermore, it has been shown that thyroid adenylate cyclase activity induced by thyrotropin was markedly depressed by excess iodide under similar experimental conditions. Therefore, it is suggested that one of the inhibitory actions of excess iodide is on the adenylate cyclase-cyclic AMP system and further, that iodide can elicit its inhibitory action after its conversion to some form of organic iodine.

Humoral and Genetic Factors in Thyrotoxic Graves Disease and Neonatal Thyrotoxicosis

WHY IS the thyroid gland hyperactive in Graves disease? Since the demise of the theory that postulated excessive pituitary thyroid-stimulating hormone secretion, most hypotheses have included some type of stimulation by immunoglobulins or activated lymphocytes, with or without a role for an intrinsic abnormality of the thyroid gland. The presence of autoimmune phenomena in Graves disease is beyond dispute. 1 Many patients have demonstrable antibodies to thyroid antigens, and Graves disease has a proved familial association with the archetypal autoimmune endocrine disease, Hashimoto thyroiditis. Graves disease is unique among so-called autoimmune diseases, however, in that an immunoglobulin that has biological effects similar to those of an important hormone, thyrotrophin, is frequently present. Since the original observation that Graves sera can produce a prolonged stimulation of thyroid secretion in guinea pigs and mice, this long-acting thyroid stimulator, or LATS, has been the object of intensive study. It is an immunoglobulin of

Activation of Thyroid Adenyl Cyclase by Antisera to Thyroid Plasma Membrane Preparations

Adenyl cyclase was assayed in a series of plasma membrane fractions prepared from bovine thyroids using sucrose density gradient ultracentrifugation. The activity of adenyl cyclase in the plasma membranes was found to be stimulated several-fold by antisera raised in rabbits against the plasma membranes and by purified IgG prepared from these antisera. The data indicate that the antibodies to thyroid plasma membrane manifest properties similar to those of the immunoglobulins long-acting thyroid stimulator (LATS) and human specific thyroid-stimulating immunoglobulin (HTSI) found in patients with Graves' disease. It is suggested that, in these patients, the antigen which leads to the production of LATS and HTSI is most likely situated in the thyroid plasma membrane.

A Reconsideration of a Thyroid-Stimulating Immunoglobulin as the Cause of Hyperthyroidism in Graves' Disease

Several assays for thyroid-stimulating immunoglobulins in the blood in patients with Graves' disease have been described recently; depending upon the method, different names have been used and distinct entities thus implied. Using an increase in cyclic AMP in the human thyroid slice after 2 h of incubation as an index of thyroid stimulation, we identified thyroid-stimulating activity in all of an unselected series of sera from 11 patients with hyperthyroidism of Graves' disease, but long-acting thyroid stimulator, by mouse bioassay, in only three. The theory is proposed that the thyroid-stimulating immunoglobulin is probably present in all such patients; it may be seen as a polyclonal antibody to a single human antigen that has a variable cross-reaction with a corresponding thyroid antigen in the mouse and in other species.

Occupational Vitiligo Caused by Paratertiary Butylphenol

To the Editor.— Occupational vitiligo caused by paratertiary butylphenol (ptBP) has been reported in the United States, the USSR, Japan, and the Netherlands. In three cases reported recently in West Germany, 1-3 there were hepatic dysfunctions, with slight increases in the serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase levels and with distinct increases in the retention of sulfobromophthalein sodium. Polymorphism of the hepatocytes and disintegration of the cytoplasm were seen in liver biopsy specimens from all three patients; specimens from two patients showed disseminated fatty degeneration. With the use of scintigraphy, enlargement of the spleen was seen in two of the patients. In all three cases, the presence of diffuse strumas was confirmed scintigraphically. Extensive functional evaluation, with the use of long-acting thyroid stimulator, disclosed intrathyroidal disorders of thyroid hormone synthesis. Antibody evaluations were positive. I believe that these are the first three cases to be reported of

Handbook of Physiology: A Critical Comprehensive Presentation of Physiologic Knowledge and Concepts

This volume admirably fulfills the promise of the general subtitle of the handbook series. It is, indeed, critical, comprehensive presentation of physiologic knowledge and concepts. Some of the general headings under which the chapters are grouped include intrathyroidal and extrathyroidal metabolism, action of the thyroid hormones, and factors affecting thyroid function. The latter section includes several superbly written chapters, especially those on the experimental and clinical aspects of iodine deficiency and iodine excess, and on the effects of radiation on thyroid function and structure. The bulk of the test is a unique blend of indepth literature review of basic thyroid physiology with some references and discussion relevant to clinical problems. Some of the reviews (eg, on thyroid iodine transport by Bastomsky, and on the long-acting thyroid stimulator by McKenzie) are excellent guides for other investigators, insofar as methodological considerations are concerned. The chapter on thyrotropin (TSH) is confined to

Human thyroid adenyl cyclase-stimulating activity in immunoglobulin G of patients with Graves' disease.

We have studied the characteristics of the stimulation of adenyl cyclase (AC) activity in human thyroid plasma membranes by thyroid-stimulating hormone (TSH) and by immunoglobulin G (IgG) from the sera of patients with Graves' disease. AC activity was measured as adenosine 3',5'-cyclic monophosphate (cAMP) generated by membranes in a 10 minute incubation. IgG from two patients with Graves' disease possessed particularly potent human thyroid AC-stimulating activity; the dose-response curves with these IgGs were essentially parallel to those obtained with TSH. As little as 30 mug of the IgG of one patient with Graves' disease or 8 muU of TSH caused significant AC stimulation. A Lineweaver-Burk plot of the data suggested similarity in the site of action of both TSH and human thyroid adenyl cyclase stimulator (HTACS) in Graves' IgG. Submaximal doses of HTACS and TSH had additive effects on AC stimulation, but a large dose of a Graves' IgG with potent AC stimulating activity did not enhance AC stimulation by a maximal dose of TSH. The effect of HTACS on AC was slower in onset and longer in duration than an equipotent dose of TSH. HTACS was detectable in IgGs of 9 of 15 untreated hyperthyroid Graves' disease patients; its concentration, however, did not correlate significantly with tests of thyroid function, nor with long-acting thyroid stimulator (LATS) activity. In another 11 treated patients with Graves' disease, selected for the presence of LATS, HTACS and LATS were significantly correlated. We observed no inhibition of LATS activity in a Graves' IgG chosen for such testing because of its high titer of HTACS and no detectable LATS. However, an inhibitor of HTACS was detected in 2 of 4 IgGs; one of these two IgGs also inhibited AC stimulation by TSH. 1) Some Graves' disease IgGs contain a human thyroid AC stimulator (HTACS), probably different from LATS. 2) HTACS may act via a common pathway with TSH; it differs from TSH, however, in having a slower onset and a greater effect during more prolonged incubation with plasma membranes. 3) There is also an inhibitor of HTACS activity in some Graves' disease IgGs.

Congenital graves disease. Four familial cases with long-term follow-up and perspective.

Congenital Graves disease has been described as a transient disorder in which the mother has or has had hyperthyroidism. Experience with four affected children to ages 5 to 9 years and a review of published cases led us to conclude that long-acting thyroid stimulator (half-life, six days) is not the cause of the disease. This disease occurs in infants from families with a high incidence of Graves disease, and, in many, hyperthyroidism persists for months or years. The pathogenesis of Graves disease is unknown, and the simplistic maternal-to-fetal humoral theory is not a suitable explanation for congenital Graves disease. If Graves disease is considered in the larger perspective than the maternal-fetal unit, a pattern of inheritance is apparent, ie, an autosomal-dominant trait with a predilection for the female individual.

Pathogenesis and therapy of neonatal graves disease.

The article by Hollingsworth and Mabry that appears in this issue of theJournal(p 148) provides interesting and important supplemental information to the authors' earlier article. 1 These articles present convincing evidence that at least some cases of congenital Graves disease (perhaps 20% to 30%) are not transient and emphasize that the disease is not benign. The mortality is in the range of 15% to 20%, and sequels, including premature synostosis and minimal brain dysfunction, are common, particularly in the cases with a persistent or recurrent course. The authors suggest that the neonatal disease is not due to transplacentally acquired long-acting thyroid stimulator (LATS), but rather that the LATS serves only as an immunologic marker or incitant in a genetically preselected population. This is a provocative hypothesis and seems credible for the infants with prolonged disease (more than six months). However, for those with transient disease of less than

Studies on the Thyrotropin Receptor in the Thyroid : Positive Cooperativity of Concanavalin A Binding and Its Biphasic Effects on Thyroid Activation Induced by Thyrotropin

Concanavalin A (Con A) was tested for its ability to affect thyroid activation induced by the thyroid stimulators in mouse thyroid tissues. Con A was found to have the biphasic stimulatory and inhibitory effects of thyrotropin (TSH)-induced cyclic AMP formation and endocytosis, a step in thyroid hormone secretion, in mouse thyroid tissues. Low concentrations of Con A potentiated TSH-stimulated cyclic AMP formation and endocytosis. In contrast, high concentrations of Con A markedly inhibited TSH stimulations. These effects were reversed by the addition of methyl-alpha-D-glucoside to the second preincubation medium (without Con A) prior to TSH. A high concentration of Con A alone did not depress the basal levels of cyclic AMP or basal glucose oxidation in thyroid tissues. A high concentration of Con A also inhibited cyclic AMP formation induced by prostaglandin E2 and the long-acting thyroid stimulator (LATS). Binding of 125I-labeled Con A to thyroid tissues increased with time up to 75 min and was very slowly reversible after attainment of equilibrium. Binding was directly proportional to tissue weight. Scatchard plot analysis on the binding of 125I-labeled Con A to thyroid tissues indicated a positive cooperativity which seemed to be well correlated to the biphasic effects.